Changes in athletic performance and physiological measures in university baseball players was assessed before, during and after a specific duration of upper cervical chiropractic care. Each athlete’s performance was evaluated through assessment of the vertical jump, broad jump specified, standing broad jump, and muscle strength. Physiological measures including blood pressure, pulse rate, microcirculation (capillary counts), and treadmill stress testing were also evaluated. Twenty one male baseball players, assigned randomly to either a control or chiropractic (adjustment) group, completed the study.The subjects were required to complete three sessions of athletic ability and physiological tests. The first session was administered before commencing chiropractic care. The second and third sessions were administered after the initiation of chiropractic care at five and fourteen weeks, respectively. Only those subjects in the adjustment group received chiropractic care. The results showed significant improvement at fourteen weeks in muscle strength and long jump distance in the group receiving adjustments. Moreover, this same group showed significant improvement in capillary counts at five and fourteen weeks of chiropractic care.Trends in decreased or increased performance in other physical and physiological measures were accompanied by either moderate or large effect sizes within both the chiropractic group and control group. Evaluation of these trends in the group receiving chiropractic care revealed decreases in resting blood pressure and pulse rate as well as pulse rate following tread mill activity. By comparison, trends in these same measures showed increases within the control group.